It is important to strengthen all of the muscles of both legs for these clients. And all clients. ACL repair usually involves using a portion of healthy ligament/tendon from another location and replacing the damaged ACL with this tissue. The outcome is dependent on many factors. The only controllable factor is the effort of the patient to rehabilitate properly. So much depends on the consistency of the patient to stick with their rehabilitation program that I would say after the skill of their surgeon and the pre-surgery condition of their fitness, the patient’s commitment to rehabilitation is the most important part of recovery.